Alkyl esters of sulfonated monohydroxy-benzoic acids



Patented Oct. 31, 1950 ALKYL ESTERSOF SULFONATED MONO- HYDROXYeBENZOIC ACIDS James 0. Harris,-Knoxville, Tenn., assignor to .Monsantofihemical Company, a corporation of D laware No Drawing. Application March 2 1947,

' Serial No. 737,428

9 Claims. (01. 260-470) The present invention relates to alkyl esters of sulionated monohydroxyebenzoic acids and to an improved process of preparing same.

The compounds contemplated by the present invention are represented by the following general formula:

ROOC- @OsYM inwhich R. is an alkyl chain of not less than 6 and not more than 18 carbon atoms or mixtures thereof asderived from alcohol obtained by the hydrogenation of coconut oil, commercially known as Lorol; Y is hydrogen, an alkali metal, calcium, magnesium, barium or strontium and m is a whole number. which may be one or esters thus formed by meansof various alkaline compounds. Thi method of operation has proved to be quite successful in practically all cases except the corresponding derivatives-of monohydroxy-benzoic acids. 7

For example, when sulfonation of orthomonohydroxy-benzoic acid is carriedo-utin .the absence of a solvent, temperatures in excess of 150 0. must be employed, which render the reaction diflicult to control with .the result .that considerable decomposition and side reactions take place. This process, therefore, results in low yield and also in the production of a crude product which presents a time-consuming and troublesome purification problem.

Ortho-monohydroXy-benzoic acid may be sulfonated at lower temperatures in an inert solvent, but the product invariably contains unre-v acted S03 which cannot be readily removed.

treated with 2-5% oleum to yield sulfo-orthohydroxy benzoic acid, but the objection to this method is that, due to the extreme solubility of the acid in water, the product yield is inordinately low. I

With regard to'the step of 'esterifying sulfoortho-hydroxy benzoic acid, all attempts to carry out this reaction have resulted in low yields of a product containing relatively large amounts of unreacted materials which not only cause discoloration of the product but render it very difficult to dry.

For example, attempts have beenmadc to react sulfoort ho-hydroxy benzoic acid with Lorol under atmospheric pressure in the presence of catalysts such as sulfuric acid, phosphoric acid and gaseous I-ICl; under reduced pressure in the presence and absence of catalysts; in the presence of toluene to remove water from the reaction by azeotropic distillation; and in the presence of a mutual solvent for the reactants, but ,in all instances it was found that the neutral equivalent fell within the range of 220 to 265 (theory 386) indicating that the reaction was only partially complete. In addition, it was found that when the esterification proceeded no further than this, the salt of the acid could not be drum dried without dis- 7 coloration.

I have found that by sulfonating the lower alkyl esters of hydroxy benzoic acids with sulfur trioxide in sufiicient quantity to'at least prod -m no ul ona ionand the sub e ting th u ona od t alco ysis by mean o an aliphatic alcohol having from 6 to 18 carbon atoms inthealhyl chain, the above disadvantages are. substantially completely eliminated. Forv example, I have made the surprising discovers tha b i g sulf t x de a h u fon in ag t t este Q h d oxy-newbie a id suc a a cy ic d d t e o r spondi meta and para-isomers thereof can be sulfonated in good yields and at a lower temperature than the .f i acids With ma ia l a f n he ester group. Moreover, I have discovered that I can obtain the desired high molecular weight esters in excellent yields and without the formationof troublesome Joy-product and unreacted starting materialswhich are encountered in the This disadvantage and the high product costs involved render sucha procedurecommercially impractical.

Ortho-hydroxy-benzoic acid may also beesterification of the free sulfo-hydroxy benzoic acids. I For] a, more complete understanding of. the present process, reference is made to the following,examples. whch lustrate the preferred embodiments of the present invention.

Example I into an esterification vessel containing 1.5 grams of HCl gas dissolved in 185.grams of Lorol which was heated to a temperature of from 60 to 70 C. The mixture thus produced was heated to 110 C., and stirred for minutes under atmospheric pressure and then under reduced pressure'for about minutes. At the end of the reaction, a sample of the product (sulfo loralky salicylate) was titrated and the neutral equivalent was found to be 333. a V

The remainder of the product was neutralized to form sodium sulfo loralkyl salicylate by means of a sufficient amount of 4% caustic soda to yield a slightly alkaline slurry. This slurry, after removal by decantation of a substantial amount of water, was drum dried and a stable light colored product was obtained.

Example II progressively added Weight Time g gg Including SO:

' Reactor Hrs. C. Grams Grams 0 25 2, 675 47 2, 720 1 111 2, 990 270 1 /1 105 3, 180 190 2 104 s, 400 220 2% 107 3, 507 107 Total 832 At the end of the reaction, the neutralization equivalent of the product was-determined and found to be 164.

2320 grams of sulfo-methyl salicylate, including practically all of the above product together with a relatively small proportion of sulfonated product prepared in another batch, was placed in a suitable reactor containing 13 grams of HCl dissolved in 1629 grams of Lorol which included a relatively small proportion of added octanol and dodecanol. The resulting mixture was then heated with stirring for 3% hours at a temperature of from 100 C. to 105 C. and at the end of the alcoholysis reaction, the product was neutralized with a caustic solution prepared by mix ing 700 c. c. of approximately NaOH with 3200 c. c. of water. The slurry of loralkyl sodium sulfo-salicylate thus obtained was then dried upon steam heated rolls under a steam pressure of from 90-100 lbs/in. and screened through A,, mesh hardward cloth. 7

2835 grams of a light colored stable product was obtained, which corresponded to a yield of 78% of theory.

The products obtained by the procedures described in Examples I and II have the following structural formula G O 0 Loralkyl NaSOa The corresponding compounds Of the meta and para isomers may be prepared by employing meta-hydroxy-benzoic acid and para-hydroxybenzoic acid respectively in the process described in the above examples. Other ester-salts may also be produced by reacting the sulfonated lower alkyl esters of ortho-, metaand para-hydroxy benzoic acid with a straight or branched chain aliphatic alcohols having from 6 to 18 carbon atoms, or mixtures of at least two of these alcohols. Moreover, although the monosulfonated derivatives are preferred, it is to be understood that the polysulfonated esters are also within the scope of the present invention.

In the-production of sulfonated lower alkyl esters of ortho-, meta-, and para-hydroxy benzoic acid, the alkyl esters and sulfur trioxide are reacted together in substantially stoichiometric proportions, the actual amount of vS03 employed depending upon the degree of sulfonation desired. In general the reaction may be carried out at a temperature ranging from about 23 C. up to a temperature at which substantial decomposition of the desired sulfonated product is avoided, but in the production of the sulfonated methyl ester, the reaction temperature is desirably maintained within the range of about 23 C. up to about 125 C. and preferably Within the range of from C. to 115 C.

- In practice, the sulfonation of the methyl ester is initiated at room temperature by introducing S03 into the liquid ester and within a relatively short time, the heat of reaction raises the temperature to about 90 C. to C. If, after 60% to 70% of the theoretical amount of gaseous 503 has been added, the reaction mixture has not reached this temperature, heat is applied until that isaccomplished. As soon as approximately 90% 0f the 503 has been introduced, the reaction is completed by heating the reaction mixture to at least to C. but not above C. while adding further amounts of S03.

The alcoholysis reaction is executed using substantially equimolecular proportions of the sulfonated lower alkyl esters of hydroxy benzoic acid and an aliphatic alcohol having from 6 to 18 carbon atoms. The reaction temperature may vary from the melting point of sulfonated alkyl ester up to a temperature at which substantial decomposition of the alcoholysis product is avoided.

In preparing sulfoloralkyl salicylate, Lorol is saturated with HCl gas, heated to about 60 C. to 70 C. and then mixed with sulfomethyl salicylate which is at a temperature of 100 C. to 115 C. The reaction mixture is then heated to about 110 C. with stirring for about 2,hours. If the neutral equivalent has not reached 330-340 at the end of this time, the reaction is continued for another half hour under reduced pressure of about 100 mm. of mercury.

The manner of mixing the reactants is not critical, but it is preferred to add the molten sulfonated methyl ester to the alcohol as improved yields are thereby obtained.

In place of HCl, up to.5% byweightof other product is dried, preferably by means of a drum drier using;.a;steampressure ofifrom 80 to 100 lbs./in. When drum drying the neutralized product, it is desirable to adjust the solids content of the slurry to at least 18 but preferably not above about 27% by weight.

In place of sodium hydroxide, other-al kalies such as sodium carbonate, sodium oxide; potas l:

sium hydroxide, potassium carbonate, potassium oxide, calcium hydroxide, calcium oxide, calcium carbonate, magnesium oxide, magnesium carbonate, barium oxide, barium hydroxide, barium carbonate, strontium oxide, strontium hydroxide and strontium carbonate may be employed.

The expression Lorol within the meaning of the present specification is intended to cover mixtures of alcohols prepared by hydrogenating coconut oil, which mixtures have an average molecular weight of about 186 (basis, dodecyl alcohol) and contain alcohols having 6 to 18 carbon atoms. The following is a typical mixture of alcohols produced by the above method.

Percent Hexyl alcohol 2 Octyl alcohol 9 Decyl alcohol 10 Lauryl alcohol n 45 Myristyl alcohol Cetyl alcohol '7 Stearyl alcohol 5 Oleyl alcohol 2 The expression loralkyl, therefore, represents the alkyl radicals derived from the above mixture of alcohols.

The expression lower alkyl as used in the specification and claims is intended to cover alkyl groups containing from 1 to 5 carbon atoms.

The expression neutral equivalent is defined by the following relationship.

Weight of acid product Volume of baseXnormality of base Neutral equivalent may also be defined as the number of grams of acid (sulfomethyl salicylate or sulfoloralkyl salicylate) neutralized by or equivalent to one mole of sodium hydroxide.

Inasmuch as the above description comprises preferred embodiments of the invention, it is to.

equimolecular proportions of a mixture of primary monohydric aliphatic alcohols obtained by the hydrogenation of coconut oil, and then neutralizing the resulting product, said alcoholysis being carried out at a temperature varying from the meltperature at which substantial decomposition' of said alcoholysis estenproduct-is avoided '2. The rocess or p'roduc'ing I aliphatic esters of sulphonated monohydroxybenzoic acid" wherein the aliphatic group is, attached to the carboxyl group, which. comprises-reacting, at 'a temperature not exceeding: 125 C.', a cor-responding dower alkyl ester with sulfur trioxide in the proportions required .to produce monosulfonation, subjectingthe sulfonated product to alcoholysis by means of substantially equimolecular proportions of a mixture of primary monohydric. aliphatic alcohols obtained byithe. hydrogenation of vcocon1 1t, 0il, and then neutralizingthe resultingproduct, said alcoholysis being carried out at a temperature varying from the melting point of said lower alkyl ester up to a temperature at which substantial decomposition of said alcoholysis-ester product is avoided.

3. The process of producing aliphatic esters of sulfonated monohydroxy benzoic acid wherein the aliphatic group is attached to the carboxyl group, which comprises monosulfonating a corresponding lower alkyl ester with sulfur trioxide at a temperature beginning with room temperature and ending with a maximum of 125 C., subjecting the sulfonated product to alcoholysis by means ofsubstantially equimolecular proportions of a mixture of primary monohydric aliphatic alcohols obtained by the hydrogenation of coconut oil, and then neutralizing the resulting product, said alcoholysis being carried out at a temperature varying from the melting point of said lower alkyl ester up to a temperature at which substantial decomposition of said alcoholysis-ester product is avoided.

4. The process of producing aliphatic esters of sulfonated ortho monohydroxy ebenzoic acid wherein the aliphatic group is attached to the carboxyl group, which comprises monosulfonating a corresponding methyl ester at a temperature of C. to 115 C'., subjecting the sulfonated product to alcoholysis with substantially equimolecular proportions of a mixture of primary monohydric aliphatic alcohols obtained by the hydrogenation of coconut oil, neutralizing the resulting product with a dilute alkaline solution and then drying the resulting slurry, said alcoholysis being carried out at a temperature varying from the melting point of said sulfonated methyl ester up to that temperature at which substantial decomposition of said alcoholysis-ester product is avoided.

5. The process of producing aliphatic esters of sulfonated salicyclic acid wherein the aliphatic group is attached to the carboxyl group, which comprises monosulfonating methyl salicylate with sulfur trioxide at a temperature within the range of room temperature up to about 107 0., subjecting the resulting sulfomethyl salicylate to alcoholysis by reaction at C.110 C. with substantially equimolecular proportions of a mixture of primary monohydric aliphatic alcohols obtained by the hydrogenation of coconut oil, neutralizing the resulting product with a dilute sodium hydroxide solution and then drum drying the resulting slurry.

6. The process defined in claim 5 wherein the alcoholysis reaction is carried out in the presence of up to 5% by weight of a mineral acid.

'7. The process defined in claim 6 wherein the alcoholysis reaction is carried out in the presence of hydrogen chloride.

8. The process defined in claim 7 wherein the alcoholysis reaction mixture is stirred for 15 minutes under atmospheric pressure and then under reduced pressure for about 30 minutes.

9. The process of producing aliphatic esters of sulfonated monohydroxy benzoic acid wherein the aliphatic group is attached to the carboxyl group, a

which comprises subjecting a corresponding sulfonated lower alkyl" ester to alcoholysis by reaction with substantially equimolecular proportions of a mixture of primary monohydric aliphatic alcohols obtained by the hydrogenation of coconut oil, and then neutralizing the resulting product, said alcoholysis being carried out at a temperature varying from the melting point of said sulfonated ester up to a temperature at which 8 substantial:decomposition of said alcoholysisester product isavoicled. 1

i L m I JAMES O. HARRIS. REFERENCES CITED 'The following references are of record in the file of this patent:

UNITED STATES PATENTS 2,380,563 V Wayo et a1. July 31, 1945 

1. THE PROCESS OF PRODUCING ALIPHATIC ESTERS OF SULFONATED MONOHYDROXY BENZONIC ACID WHEREIN THE ALIPHATIC GROUP IS ATTACHED TO THE CARBOXYL GROUP, WHICH COMPRISES REACTING, AT A TEMPERATURE NOT EXCEEDING 125*C., A CORRESPONDING "LOWER ALKYL" ESTER WITH SULFUR TRIOXIDE IN SUBSTANTIALLY THE THEORETICAL PROPORTIONS REQUIRED TO PRODUCE AT LEAST MONOSULFONATION, SUBJECTING THE SULFONATED PRODUCT TO ALCOHOLYSIS BY MEANS OF SUBSTANTIALLY EQUIMOLECULAR PROPORTIONS OF A MIXTURE OF PRIMARY MONOHYDRIC ALIPHATIC ALCOHOLS OBTAINED BY THE HYDROGENATION OF CONCONUT OIL, AND THEN NEUTRALIZING THE RESULTING PRODUCT, SAID ALCOHOLYSIS BEING CARRIED OUT AT A TEMPERATURE VARYING FROM THE MELTING POINT OF SAID "LOWER ALKYL" ESTER UP TO A TEMPERATURE AT WHICH SUBSTANTIAL DECOMPOSITION OF SAID ALCOHOLYSIS-ESTER PRODUCT IS AVOIDED. 